How long does bare copper pcbs usually last?

[marlo830]

I've etched about 5 boards and didn't bother tinning them with Flux + Solder. It just crossed my mind and started wondering how long do bare Cu pcbs generally last.

[deadastronaut]

give them a shot of spray clear coat.....you can solder through it still....

[bool]

...
and started wondering how long do bare Cu pcbs generally last
...

They last just as long as the metal shines.

[marlo830]

give them a shot of spray clear coat.....you can solder through it still....

How bout clear nail polish? I read somewhere it can be used to coat the traces.

[Mark Hammer]

How long depends on the environment.  Some climates expedite oxidation more than others.  You can provide some reasonable protection from the environment by storing them in an envelope.  If you have lots of envelopes, consider labelling each with the specific board enclosed, and sealing it.

I generally buff my boards and apply liquid flux with a cotton swab right away.  I may or may not tin them with normal solder at that point.  The flux provides a barrier against oxidation, and from what I can tell, the metals in solder don't oxidize nearly as quickly as bare shiny copper.  They WILL eventually, just more slowly.

[deadastronaut]

give them a shot of spray clear coat.....you can solder through it still....

How bout clear nail polish? I read somewhere it can be used to coat the traces.

hmmmm never tried it, might be too thick and gloopy to apply.......the spray clear goes on even...
it only needs a quick spurt....

[Rob Strand]

I've etched about 5 boards and didn't bother tinning them with Flux + Solder. It just crossed my mind and started wondering how long do bare Cu pcbs generally last.

If you leave them to oxidize they can be cleaned up later.  For home use it works fine.  Just don't keep cleaning them.   The only thing you have to watch out for is the oxide around the holes - the important area!  Often they don't clean-up as well as the larger areas of copper.

Much preferred is:

the spray clear goes on even... it only needs a quick spurt....

I used that method for 30 years for home one-offs.   I have boards which must be getting onto 30 years old and they are still clean.   I did experiment with different coating thicknesses at one point.  Too thin and it can be patchy, sometimes having holes on a small scale and later showing minor oxidation.   Too thick and you get goop around the pads when soldering.   I guess the instructions would say a light coating.

Many moons ago there was a PCB manufacturer around here that did simple one-sided boards.   They did small runs and kept a small number of boards from magazines projects in stock.  They use the light clear lacquer on the bottom of their boards.

For professional products you not only have finished boards but they should be stored vacuum sealed (and they should not be touched by people's fingers at all).

[Mark Hammer]

I used that method for 30 years for home one-offs.   I have boards which must be getting onto 30 years old and they are still clean. 

Now, do you remember what those 30 year-old boards are FOR?  I have some of similar vintage.  I know that they are for something from either Popular Electronics, Radio Electronics, or Electronics Today, and I know it's probably something audio-related, but that's pretty much as far as I can narrow it down.   

[Rob Strand]

Now, do you remember what those 30 year-old boards are FOR?

One was a prototype capacitance meter.  Another was an AC phase controller (essentially a light dimmer).
There's other stuff kicking around which are loaded boards but I sprayed the board the same way *before* assembling them.  So from the point of view of oxidation they are in the same boat - except for solderability.

Now I think of it another thing I tried was drilling before etching.   Not sure why  , maybe used the track design as a drill template - this was the bad old days before laser printers.  I remember the etchant oxidized around the hole and it was very hard to clean-up.

[bluebunny]

Now, do you remember what those 30 year-old boards are FOR?  I have some of similar vintage.  I know that they are for something from either Popular Electronics, Radio Electronics, or Electronics Today, and I know it's probably something audio-related, but that's pretty much as far as I can narrow it down.   

Sounds like an intriguing detective thread, waiting to happen.      Post some pictures!  Ya never know...

[deadastronaut]

^ yay, a game of guess the circuits....

[Mark Hammer]

Happily, both Francisco Pena and madbean have the name of the circuit on all their PnP layouts.  So, if I make it into my 90s, am still soldering, and still have the boards, I'll know what they are. 

[ElectricDruid]

I've etched about 5 boards and didn't bother tinning them with Flux + Solder. It just crossed my mind and started wondering how long do bare Cu pcbs generally last.

If you leave them to oxidize they can be cleaned up later.  For home use it works fine.  Just don't keep cleaning them.   The only thing you have to watch out for is the oxide around the holes - the important area!  Often they don't clean-up as well as the larger areas of copper.

+1 agree. You can make oxidised PCBs workable by attacking them with fine wire wool. The stuff with soap in it as well is fine since the soap removes any greaser while you're at it. Once you're done, rinse them well with cold water and dry them off and you're good. Rob's comment about the holes being the hardest bit to get cleaned up is valid.

[Rob Strand]

holes being the hardest bit to get cleaned up is valid.

A good strategy would be to shelve them undrilled.

[marlo830]

Thanks for all of your insights! Decided to tin an unpopulated MiniBomb from EffectsLayout blog, made drilling much more easier and soldering components (duh) as well. Might try the clearcoat method if I find time or might as well just create new pcbs cause I find it fun to do.

[davent]

Thanks for all of your insights! Decided to tin an unpopulated MiniBomb from EffectsLayout blog, made drilling much more easier and soldering components (duh) as well. Might try the clearcoat method if I find time or might as well just create new pcbs cause I find it fun to do.

If your only issue with those earlier pcb's is oxidation and you haven't partially populated them, it's a simple matter to clean them up with wet 600 grit sandpaper backed with a hard block. Then can give them a quick light mist of clearcoat so they don't re-oxidize, clearcoat works great.
dave